Northeastern States Research Cooperative

RELATED PUBLICATIONS:

Hales, H.C., D.S. Ross, and A. Lini. 2007. Isotopic signature of nitrate in two contrasting watersheds of Brush Brook, VT. Biogeochemistry 84:51-66.

Pardo, L.H., P.H. Templer, C.L. Goodale, S. Duke, P.M. Groffman, M.B. Adams, P. Boeckx, J. Boggs, J. Campbell, B. Colman, J. Compton, B. Emmett, P. Gundersen, Kjønaas, G. Lovett, M. Mack, A. Magill, M. Mbila, M. J. Mitchell, G. McGee, S. McNulty, K. Nadelhoffer, S. Ollinger, D. Ross, H. Rueth, L. Rustad, P. Schaberg, S. Schiff, P. Schleppi, J. Spoelstra, and W. Wessel. 2006. Regional assessment of nitrogen saturation using foliar and root ?15N. Biogeochemistry 80(2):143-171.

Ross, D.S. 2007. A carbon-based method for estimating the wetness of forest surface soil horizons. Canadian Journal of Forest Research 37:846-852.

Ross, D.S., B. Fredriksen, A.E. Jamison, B.C. Wemple, S.W. Bailey, J.B. Shanley, and G.B. Lawrence. 2006. One-day rate measurements for estimating net nitrification potential in humid forest soils. Forest Ecology and Management 230:91-95.


	Forest Soil Nitrogen Transformations Related to Tree Species and Soil Carbon

2002 *Nitrification Rates across NERC Sites: Temporal Variability, Riparian Sources, and Predictive Ability*

Donald Ross University of Vermont dross@uvm.edu

Beverley Wemple University of Vermont Guinevere Fredriksen Cornell University, NY Scott Bailey and John Campbell USDA Forest Service, Northern Research Station, NH James Shanley U.S. Geological Survey, VT Gregory Lawrence U.S. Geological Survey, NY

Nitrogen is the major component of the Earth’s atmosphere and an essential element for many biological processes. Most of the nitrogen in the air is not available for biological use but, over the past decades, burning of fossil fuels has contributed to elevated available nitrogen coming down in precipitation as part of acid rain. However, it is difficult to assess the effects of this increase because the deposited nitrogen is rapidly transformed in forest soils and difficult to trace. To gain a better understanding of the effects of increased nitrogen in forest soils, NSRC researchers are studying a portion of nature’s nitrogen cycle called nitrification. Nitrification is the conversion of ammonium into nitrates by soil bacteria. Researchers collected soil samples from forested watersheds in New York, Vermont, and New Hampshire and compared rates of nitrification with measurements of tree species, topographic features, and other soil properties. The effort was both to test the nitrification method over different seasons and to determine factors common to all sites that affected the rates. A 1-day test method was reliable even when used at different times of the year. Nitrification rates appeared to depend on the distribution of tree species, with lower rates where conifer species made up a greater portion of the tree biomass. Rates were also related to the ratio of carbon to nitrogen in the soil. Both of these factors have been found in other studies, but this research clarified relationships and contributed to our understanding of the biogeochemical effects of human impacts on the Northern Forest.